95 Corolla miss at idle

[appelserv]

Please help!
I'm working on a 95 Corolla, 1.8L with EFI(7AFE engine). Engine cranks fine but dies out intermittently at idle speed. It seems to happen more frequently after engine warms. ECU is showing no trouble codes. I have replaced timing belt and tested engine timing, replaced plugs, plug wires, rotor, tested distributor components, removed and cleaned fuel injectors, throttle body, and plenum air chamber. No indication of vacuum loss. What else do I try before submerging in the nearest body of water?

[wrench234]

it could be an idle air control problem may also be air flow meter causing your problem do you have a scanner where you could read data or maybe take a snapshot while problem is occuring

[appelserv]

I've tested the idle control valve per the Haynes service manual. Appears to be operating properly. Are you referring to the ECU in reference to the air flow meter or the manifold pressure sensor which also is within spec?

[wrench234]

i was thinking that this car might of had a mass air flow sensor most foriegn car companys call it an air flow meter but it doesnt seem that it does the ecm relies on the map sensor only you said it happens mostly when warm is the car equipped with a/c there is a seperate idle up valve to raise the idle when the a/c is operating how intermitant is the problem can you duplicate it easily sometimes when you are testing readings may be ok with an intermittant problem have you tried wiggle and tap testing electrical components and wiring while the engine is running to see if you can get the problem to occur that way

[appelserv]

The a/c idle up valve is working ok. The engine actually seems to idle better with the a/c on. I just finished re-testing the fuel pump. Also rerouted fuel from the fuel return to drain the fuel tank. I'm wondering if the fuel was contaminated at some point and residual effects are popping up. I did replace the throttle position sensor when the throttle body was removed and cleaned. The old unit was virtually impossible to set per specs. Is it possible that I haven't given the ecu enough run time to adjust? STILL OPEN TO SUGGESTIONS!!!

[tashirosgt]

I suppose you did a compression test and measured fuel pressure. How did you test the injectors when you removed them?

[appelserv]

No, I didn't do a cylinder compression test, but fuel pressure is within spec (37 lb). Injectors were tested with compressed air while energizing solenoid with a battery.

[appelserv]

I finally tracked problem back to the ignition coil. All hot and cold specs were within range when checking resistance, however I pulled the distributor for the third time and examined under magnifying lens. Found a small pit in epoxy on top of coil where it was breaking down intermittently at operating temp. Good to have my rolla back.